Hydroquinone

123-31-9

Hazard Summary-Created in April 1992; Revised in January 2000

Hydroquinone is used as a developing agent in photography and as an antioxidant
in rubber and food. Tinnitus (ringing in the ears), dizziness, headache,
nausea, vomiting, dyspnea, erosion of the gastric mucosa, edema of internal
organs, cyanosis, convulsions, delirium, and collapse may result from
the ingestion of a large amount of hydroquinone in humans. Hydroquinone
is also a skin irritant in humans. Chronic (long-term) occupational
exposure to hydroquinone dust can result in eye irritation, corneal effects,
and impaired vision. No information is available on the reproductive,
developmental, or carcinogenic effects of hydroquinone in humans.
There was some evidence of carcinogenic activity in orally-exposed rodents.
Increased skin tumor incidence has been reported in mice treated dermally.
EPA has not classified hydroquinone for carcinogenicity.

Uses

Hydroquinone is used as a developing agent in black-and-white photography,
lithography, and x-ray films. It is also used as an intermediate
to produce antioxidants for rubber and food. It is added to a
number of industrial monomers to inhibit polymerization during shipping,
storage, and processing. (2,7)

Sources and Potential Exposure

Occupational exposure to hydroquinone may occur by inhalation or
dermal contact. (1)

Hydroquinone is released to the atmosphere from its production and
use, such as during methyl methacrylate manufacture and in the production
of coal-tar chemicals. (1,2)

It may be released in the effluent of photographic processes and
from coal gasification condensate water. (1,2)

Individuals who develop black-and-white film may be exposed to hydroquinone,
as it is a common component of developing solutions. (1)

Hydroquinone has been detected in cigarette smoke and in diesel engine
exhaust. (2)

Assessing Personal Exposure

No information was located regarding the measurement of personal
exposure to hydroquinone.

Health Hazard Information

Acute Effects:

Tinnitus (ringing in ears), dizziness, headache, nausea, vomiting,
dyspnea (labored breathing), erosion of the gastric mucosa, edema of
internal organs, cyanosis (bluish coloration of the skin due to lack
of oxygen in the blood), convulsions, delirium, and collapse may result
from the ingestion of a large amount of hydroquinone in humans. (1-3)

Acute (short-term) animal tests in rats, mice, and rabbits have demonstrated
hydroquinone to have high acute toxicity
from oral exposure. (4)

Chronic Effects (Noncancer):

Chronic occupational exposure to hydroquinone dust has resulted in
eye injuries, which varied from mild irritation and staining of conjunctivae
and cornea to changes in the thickness and curvature of the cornea,
loss of corneal luster, and impaired vision; prolonged exposure is required
for the development of severe ocular effects. (2)

Nausea, vomiting, abdominal cramps, and diarrhea occurred in humans
who chronically consumed water contaminated with hydroquinone.
However, in one study, no effects on the blood or urine parameters tested
were observed in people who voluntarily ate low doses of hydroquinone
for less than 6 months. (2)

Rats chronically exposed via gavage (experimentally placing the chemical
in the stomach) suffered from tremors and convulsions and death at the
highest levels, as well as effects on the kidneys and stomach, and forestomach
lesions were reported in mice. Rats exposed to hydroquinone in
their diet ate less, lost weight, and developed aplastic anemia.
Rats that consumed the chemical in their water gained weight more slowly;
developed slight blood effects and dystrophic changes in the small intestines,
liver, kidneys, and myocardium; and had increased liver and kidney weights.
In several animal studies, no significant health effects were noted.
(2,7)

EPA has not established a Reference Concentration (RfC)
for hydroquinone. (5)

EPA has calculated a provisional Reference Dose (RfD)
of 0.04 milligrams per kilogram body weight per day (mg/kg/d) for hydroquinone
based on hematological effects in humans. The provisional RfD
is a value that has had some form of Agency review but is not on the
Integrated Risk Information System (IRIS). The RfD
is an estimate (with uncertainty spanning perhaps an order of magnitude)
of a daily oral exposure to the human population (including sensitive
subgroups) that is likely to be without appreciable risk of deleterious
noncancer effects during a lifetime. It is not a direct estimator
of risk but rather a reference point to gauge the potential effects.
At exposures increasingly greater than the RfD,
the potential for adverse health effects increases. Lifetime exposure
above the RfD does not imply
that an adverse health effect would necessarily occur. (6)

Reproductive/Developmental Effects:

No information is available on the reproductive or developmental
effects of hydroquinone in humans.

A slight reduction in maternal body weight gain, decreased fetal
weight, increased resorption rate, and reduced fertility in males have
been observed in rats orally exposed to hydroquinone via gavage or in
the diet. (2)

In a National Toxicology Program (NTP) study of rats and mice dosed
by gavage, there was some evidence of carcinogenic activity for male
rats, as shown by increases in tubular cell adenomas of the kidney;
there was some evidence of carcinogenic activity for female rats, as
shown by increases in mononuclear cell leukemia; there was no evidence
of carcinogenic activity for male mice; there was some evidence of carcinogenic
activity for female mice, as shown by increases in hepatocellular neoplasms.
(1,7,8)

Health Data from Inhalation Exposure

ACGIH TLV--American Conference of Governmental and Industrial
Hygienists' threshold limit value expressed as a time-weighted average;
the concentration of a substance to which most workers can be exposed
without adverse effects. NIOSH REL ceiling--National Institute of Occupational Safety and
Health's recommended exposure limit ceiling; the concentration that should
not be exceeded at any time. NIOSH IDLH -- NIOSH's immediately dangerous to life or health concentration;
NIOSH recommended exposure limit to ensure that a worker can escape from
an exposure condition that is likely to cause death or immediate or delayed
permanent adverse health effects or prevent escape from the environment.
OSHA PEL--Occupational Safety and Health Administration's permissible
exposure limit expressed as a time-weighted average; the concentration
of a substance to which most workers can be exposed without adverse effect
averaged over a normal 8-h workday or a 40-h workweek.

The health and regulatory values cited in this factsheet were obtained
in December 1999.aHealth numbers are toxicological numbers
from animal testing or risk assessment values developed by EPA. bRegulatory numbers are values that have been
incorporated in Government regulations, while advisory numbers are nonregulatory
values provided by the Government or other groups as advice. OSHA numbers
are regulatory, whereas NIOSH and ACGIH numbers are advisory.

National Institute for Occupational Safety and
Health (NIOSH). Pocket
Guide to Chemical Hazards. U.S. Department of Health and
Human Services, Public Health Service, Centers for Disease Control and
Prevention. Cincinnati, OH. 1997.